Document LDAP-keystone hardening

Added instructions on how to secure the connection between the
keystone host and LDAP server. This patch also includes some edits to
the instructions for setting up Assignments, among them is
splitting it off to a different XML file (for easier management).

Change-Id: I63c19bc034d52efd9e7235c14cd3f0d78d5ae275
Closes-Bug: #1290605
Add dev docs redirect for sahara client too

Change-Id: I860e2806cad9e0b62e35cfe297ff3e8a82ea6a6f
Merge "Document LDAP-keystone hardening"
Merge "Add dev docs redirect for sahara client too"